Change width of menu and margins

I'd like to change the width of the margin on the right hand side of my blog so that it is the same as the margin on the left, and have the width of the menu bar in line with the text below on the right hand side (at the moment it doesn't align).

Hi, to widen the header/menu to the width of the content and align it on the right with the text in the sidebar, make the following changes in the #masthead rule you have in your custom CSS. On the width declaration you have, change that to max-width and 100%.